The invention relates to an optical switch for the transmission of unpolarized light from an input optical fibre to one of several output optical fibres via an input lens system and an output lens system whereto the input and output fibres, respectively are optically coupled, and via at least one electrically controllable nematic crystal which determines, under the influence of an adjustable electric field, a path to be followed by the light between the input lens system and the output lens system, the switch comprising an optical device for dividing unpolarized light into two beams of linearly polarized light whose polarization directions are orthogonal.
An optical switch of this kind is known from "Applied Optics", Vol. 19, No. 17, September 1980, pages 2921-2925. This described optical switch is limited to two positions. Ths light from an input fibre is switched either to a second or to a third output optical fibre. For the switching of light from an input fibre to four eight or more output fibres, three, seven or even more switches of the described kind are required. This is a drawback, because the described switches are comparatively expensive.
It is an object of the invention to provide a switch whereby the light can be switched from one input fibre to any one of several output fibres.
To this end, the optical switch in accordance with the invention is characterized in that the switch comprises an optical element for rotating the polarization direction of one of the beams of linearly polarized light through an angle of 90.degree., the output fibres being arranged adjacent one another behind a single output lens system. In a switch of this kind, the linearly polarized light is deflected by the nematic crystal to an extent dependent on the intensity of the control voltage applied thereto, so that the light is directed, via the lens system, to one of several, for example from 3 to 8, adjacently situated output optical fibres.